Substitute provided by bankers at Zurich (6)
I believe the answer is:
ersatz
'substitute' is the definition.
(I know that ersatz is a type of substitute)
'provided by bankers at zurich' is the wordplay.
'provided by' says the answer is hidden in the clue (the answer is provided within the clue).
'ERSATZ' is hidden within 'bankers at zurich'.
(Other definitions for ersatz that I've seen before include "Mock" , "Cheap substitute or imitation" , "Spurious" , "Not real or genuine" , "Imitation, not the real thing" .)